The technique of drill stem testing is conventionally employed to evaluate the production potential of selected zones in the earth formations of a well, prior to completion. The usual practice has been to assemble the drill stem test equipment in the lower end of the drill pipe and run it into the well. The apparatus would include a releasable packer that can be set by manipulation of the drill pipe to isolate the formation under test from the well bore annulus around the drill pipe above the formation. The apparatus would also include valve means controlled by manipulation of the drill pipe to permit flow of fluid from the formation into the drill pipe and to above ground equipment or to shut off such flow. The apparatus would further include pressure sensor and recorder devices. A part of the drill stem test involves making a record of the pressures encountered by the pressure sensor devices under various conditions. Since there is no concurrent surface indication of the pressures, it is necessary to estimate or guess at certain of the time intervals involved. For example, when the formation flow is shut in, the time it takes to reach a steady state formation pressure must be guessed at. If insufficient time is allowed, erroneous information or inadequate information is obtained. If too much time is allowed, then, valuable rig waiting time is expended. It is, thus, apparent that there is a need to provide a concurrent surface indication of earth formation characteristics, such as the pressures encountered by appropriate fluid pressure sensors in the course of a drill stem test. Some efforts have been made along these lines, as exemplified by U.S. Pat. No. 3,041,875, but the results have not proved to be entirely satisfactory.
It is, accordingly, an object of this invention to devise improved apparatus and methods to provide concurrent surface indications of earth formation characteristics during drill stem testing operations.
There is also a need to provide for concurrent surface indications of earth formation characteristics during similar testing operations in production wells, and it is a further object of this invention to provide improved methods and apparatus to accomplish this purpose.
For a further understanding of the invention and further objects, features, and advantages thereof, reference may now be had to the following description, taken in conjunction with the accompanying drawings.